Stressed medical students and Lactobacillus casei strain Shirota

"Our findings indicate that the daily consumption of probiotics such as LcS [Lactobacillus casei strain Shirota] preserves the diversity of the gut microbiota and may relieve stress-associated responses of abdominal dysfunction in healthy subjects exposed to stressful situations."

So said the findings reported by Akito Kato-Kataoka and colleagues [1] who following the use of a "double-blind, placebo-controlled trial" method were able to potentially offer "healthy medical students undertaking an authorized nationwide examination for promotion" a leg up when it came to minimising / overcoming stress-induced abdominal dysfunction. As many people might have themselves experienced, exam stress can sometimes manifest in various different ways...

With some of the authors working at the Yakult Central Institute (originally called the Shirota Research Institute after one of the most famous men to have a bacterial strain named after them), researchers followed nearly 50 medical students for 8 weeks "until the day before the examination", half consuming "a LcS-fermented milk" and half "a placebo milk daily." Various measures looking at abdominal symptoms, "psychophysical state" and salivary stress compounds were included in the study as well as composition of the gut microbiota "analyzed using DNA microarray and 16S rRNA gene amplicon sequence analyses."

Results: well you already know what conclusion was reached but a bit more on the details: "The administration of LcS, but not placebo, significantly reduced gastrointestinal symptoms." It's also not beyond the realms of possibility that this 'bowel' finding was also linked to a wider diversity of gut bacterial species found in the experimental (LcS) group over the placebo group. It is also reported that the placebo group showed a "significant increase in salivary cortisol levels before the examination." Quite a few potential positive for the LcS-fermented milk and importantly, few, if any side-effects.

I note that this is not the first time that the use of LcS has been reported on with medical students and stress in mind as other peer-reviewed papers demonstrate [2] (open-access here). Indeed, this is the same cohort talked about in today's discussion paper and complement findings with details such as "the LcS group had significantly higher faecal serotonin levels (P<0.05) than the placebo group." And if you want some animal findings too [3] look no futher...

If I were to start being a little more speculative about the Kato-Kataoka data and implications outside of just medical students under exam stress, I might be inclined to suggest that this is good evidence for the possibility of a connection between the trillions of wee beasties that populate our digestive tract (the gut microbiome) and brain and behavioural functions. Y'know, the gut-bacteria-brain axis that is so popular these days (see here for example). If it is at all likely that medical students are not a million miles away from other groups of people in terms of physiology, the idea that stress manifesting as abdominal dysfunction could be to some degree countered by ingestion of a probiotic, I'd say that there are quite a few important studies to be done. In fact [4]...

And perhaps related to today's musings, an interesting discussion about irritable bowel syndrome (IBS) not being 'all in the mind'.

To close, I know I've not posted much music these past few weeks so to make up for it a film showing British community policing at it's very best...

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[1] Kato-Kataoka A. et al. Fermented milk containing Lactobacillus casei strain Shirota preserves the diversity of the gut microbiota and relieves abdominal dysfunction in healthy medical students exposed to academic stress. Appl Environ Microbiol. 2016 May 6. pii: AEM.04134-15.

[2] Kato-Kataoka A. et al. Fermented milk containing Lactobacillus casei strain Shirota prevents the onset of physical symptoms in medical students under academic examination stress. Benef Microbes. 2016 Mar 11;7(2):153-6.

[3] Takada M. et al. Probiotic Lactobacillus casei strain Shirota relieves stress-associated symptoms by modulating the gut-brain interaction in human and animal models. Neurogastroenterol Motil. 2016 Feb 20.

[4] Diop L. et al. Probiotic food supplement reduces stress-induced gastrointestinal symptoms in volunteers: a double-blind, placebo-controlled, randomized trial. Nutr Res. 2008 Jan;28(1):1-5.

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Kato-Kataoka A, Nishida K, Takada M, Kawai M, Kikuchi-Hayakawa H, Suda K, Ishikawa H, Gondo Y, Shimizu K, Matsuki T, Kushiro A, Hoshi R, Watanabe O, Igarashi T, Miyazaki K, Kuwano Y, & Rokutan K (2016). Fermented milk containing Lactobacillus casei strain Shirota preserves the diversity of the gut microbiota and relieves abdominal dysfunction in healthy medical students exposed to academic stress. Applied and environmental microbiology PMID: 27208120